1. Field of the Invention
The present invention relates to a wirelessly-connectable imaging system and a method of controlling the imaging system. In particular, it relates to a suitable technique used for a wirelessly-connectable imaging apparatus and peripheral devices thereof.
2. Description of the Related Art
Conventionally, controlling systems is performed by an optical or wireless communication connection between devices in various fields. For example, it is known that an imaging apparatus and a flash device as a peripheral device of the imaging apparatus are connected via an optical signal to control light emission. In another case, instead an optical signal, a wireless communication using a radio wave of 2.4 GHz, referred to as the Industry Science Medical (ISM) band, is used. Since end-users can use the ISM band without authorization, the ISM band is used in various fields.
Japanese Patent Application Laid-Open No. 2000-089306, for example, discusses an imaging apparatus that uses optical communication to execute light emission control. More specifically, the technique uses a light emission pulse of a flash device for optical communication connection between a master imaging apparatus and a slave flash device. Since this technique uses visible light having a short wavelength, the directivity is great. As a result, if an obstacle or the like is present between the master imaging apparatus and the slave flash device, accurate optical communication may not be executed.
Japanese Patent Application Laid-Open No. 2003-218763 discusses a wireless communication system that uses a wireless communication standard referred to as Bluetooth® to connect mobile phones or to connect a mobile phone and a printer. Japanese Patent Application Laid-Open No. 2002-335254 discusses an electronic conference system that uses the Bluetooth® wireless communication standard to wirelessly connect a master terminal and a slave terminal.
Since the techniques discussed in Japanese Patent Application Laid-Open No. 2003-218763 and Japanese Patent Application Laid-Open No. 2002-335254 use a radio wave, the wavelength is longer and the directivity is wider than light. Thus, signals can easily reach around and behind obstacles by diffraction. While relatively less influenced by such obstacles or the like, the communication system is restricted by conditions unique thereto.
For example, in a small-sized network referred to as a piconet, which is defined by the Bluetooth® wireless standard and thus not described in detail herein, the maximum number of slave devices that can simultaneously be connected is seven.
If more than eight slave devices are present, seven slave devices are set to be active, and the other slave devices are set to a standby mode referred to as a park mode. Namely, the slave devices are connected by being switched between active and park as needed. Thus, the above Japanese Patent Application Laid-Open No. 2003-218763 discusses displaying a warning message or the like when more than eight slave devices are present.
An electronic conference system, as discussed in the Japanese Patent Application Laid-Open No. 2002-335254. sequentially switches active and park when more than seven slave devices are present. However, if this wireless system is applied to an imaging system with flash devices, inappropriate switching may impact the imaging process.